Behavioral assays of western corn rootworm larvae to perform RNAi-mediated knockdown of CO2 receptors expression

CO₂ has been identified as an important host-finding cue for WCR larvae. RNAi-mediated knockdown of the CO₂ receptor transcripts has been explored as possible mechanism to disrupt host-finding behavior and protect corn plants from larval feeding damage. Laboratory bioassays of WCR larval response to CO₂ and corn roots need to be developed to evaluate the effect of the knockdown of CO₂ receptor expression on larval host-finding behavior. The goal of this research was to develop a behavioral assay of WCR larval response to CO₂ and corn roots. The  methodology consists in an olfactometer with three individual treatments: CO₂, corn roots and air.  Larvae were exposed to the treatments for one minute using an airflow from the odor sources of 10ml/min. After this, larvae were exposed to the treatments with no airflow for one hour in the dark. A total of 20 larvae were evaluated per replication. The number of larvae that choose the treatment and the distance traveled were recorded at one hour after the exposure to the treatments. There were significant differences between the CO₂ and corn seedlings with the control. The application of this methodology on the evaluation of the knockdown of CO₂ receptors and the implications on host-finding behavior of WCR larvae will be discussed.